(a) Field of the Invention
This invention pertains generally to the field of fluid switching valve for selectively directing fluid flow through alternate flow paths and in particular, to drives for actuating up-down slide valves in filter backwash system or in fluid flow switching in solar collector systems, among many possible applications.
(b) Description of the Prior Art
Various types of switching valves are widely used to control fluid flow through filter media, e.g., sand media filters in swimming pool installations, in various industrial installations as well as for controlling direction of fluid flow in solar heating fluid circuits. The valves in use include both manually activated valves as well as motor driven valves provided with automated controls of varying complexity.
Particularly common are the so-called "slide-up-down valves" or vertical backwash valves. These relatively simple and economical devices generally comprise a cylindrical metallic or plastic valve body defining a cylindrical bore with a plurality of ports formed in the cylinder wall. A coaxial shaft axially movable within the valve bore, carries two, three, or more discs provided with O-ring seals for partitioning the valve bore at selected points into chambers having various ports; these chambers then permit fluid flow between selected pairs of ports. The shaft carrying the sealing O-rings is axially movable between two positions, each position establishing a different set of interconnections between the ports, and can thus achieve a flow switching action by sliding the valve shaft from one position to the other.
Originally, up-down slide valves were manually operated. This is often a slow and tedious task because the seal rings tend to adhere to the wall of the valve bore when the valve is left in its normal flow position for prolonged periods of time and, during which mineral deposits tend to form within the valve bore making it difficult to dislodge the O-rings and move the valve shaft of the slide valve.
Various attempts have been made to construct motor driven switching valves of this type. While such units have been marketed, none have proved entirely satisfactory in performance, reliability and economy.
The valve drive means disclosed by this specification provides a reliable and economical mechanism of simple construction and effective operation which has been found superior to those known in the past. The valve drive means disclosed herein may be quickly and easily attached to many existing up-down valves for conversion from manual to automated operation. Applicant is not aware of any drive means of the prior art suitable for such conversion.